What is Johne’s disease?

Johne’s disease is an infectious bacterial disease of cattle and other ruminants. The infecting bacteria is known as MAP. Cattle usually become infected during the early weeks of life following the consumption of milk or food contaminated with the bacteria, which are shed in the dung or milk of infected adult cattle. Infection develops slowly (months to years) and the signs of disease vary depending upon the stage of infection but begin with reduced productivity followed by weight loss, scour and ultimately emaciation and death.
Extra Information:

It has been speculated that the MAP ( Mycobacterium avium subsp. paratuberculosis ) bacteria that causes Johne’s Disease in cattle is also associated with the human disease, Crohns. However, the current evidence does not support a causal relationship. In addition, pasteurisation is a well established food safety measure, which is implemented nationally to reduce potentially harmful bacteria that could naturally be present in milk.
Is the somatic cell count of milk an indicator of a cow’s health?

As the somatic cell count (SCC) is an indicator of infection, it is an acceptable indicator of a cow’s udder health, particularly in relation to the presence of mastitis. However, a more comprehensive assessment of a cow’s health should take many other factors into consideration such as physical appearance (e.g. demeanour, body weight, shape, coat appearance, and gait), growth rate, biochemical analysis, milk yield and stool consistency.